CN113511634B - System and method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in steel industry through pickling - Google Patents
System and method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in steel industry through pickling Download PDFInfo
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- CN113511634B CN113511634B CN202110499663.2A CN202110499663A CN113511634B CN 113511634 B CN113511634 B CN 113511634B CN 202110499663 A CN202110499663 A CN 202110499663A CN 113511634 B CN113511634 B CN 113511634B
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 title claims abstract description 126
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 title claims abstract description 103
- 229910000360 iron(III) sulfate Inorganic materials 0.000 title claims abstract description 92
- 239000002699 waste material Substances 0.000 title claims abstract description 38
- 150000003839 salts Chemical class 0.000 title claims abstract description 33
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 29
- 239000010959 steel Substances 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000004064 recycling Methods 0.000 title claims abstract description 27
- 238000005554 pickling Methods 0.000 title claims abstract description 18
- 238000010521 absorption reaction Methods 0.000 claims abstract description 275
- 239000007788 liquid Substances 0.000 claims abstract description 164
- 239000013078 crystal Substances 0.000 claims abstract description 85
- 239000007789 gas Substances 0.000 claims abstract description 84
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 80
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 77
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 claims abstract description 76
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 60
- 239000000843 powder Substances 0.000 claims abstract description 33
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000001035 drying Methods 0.000 claims abstract description 15
- 238000001914 filtration Methods 0.000 claims abstract description 13
- 230000001590 oxidative effect Effects 0.000 claims abstract description 7
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims abstract 3
- 239000007921 spray Substances 0.000 claims description 102
- 238000012856 packing Methods 0.000 claims description 81
- 239000000945 filler Substances 0.000 claims description 64
- 239000000428 dust Substances 0.000 claims description 53
- 238000001816 cooling Methods 0.000 claims description 37
- 239000004744 fabric Substances 0.000 claims description 35
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 30
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 22
- 239000002253 acid Substances 0.000 claims description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 18
- 239000003345 natural gas Substances 0.000 claims description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 239000008213 purified water Substances 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 230000009471 action Effects 0.000 claims description 10
- 238000002485 combustion reaction Methods 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 238000007599 discharging Methods 0.000 claims description 7
- 230000000903 blocking effect Effects 0.000 claims description 6
- 229910000358 iron sulfate Inorganic materials 0.000 claims description 6
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 2
- 238000000889 atomisation Methods 0.000 claims 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 abstract description 11
- 239000002994 raw material Substances 0.000 abstract description 8
- 238000009628 steelmaking Methods 0.000 abstract description 4
- 230000004044 response Effects 0.000 abstract description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 18
- 229960005191 ferric oxide Drugs 0.000 description 18
- 238000000354 decomposition reaction Methods 0.000 description 11
- 239000006096 absorbing agent Substances 0.000 description 10
- 229910001220 stainless steel Inorganic materials 0.000 description 9
- 239000010935 stainless steel Substances 0.000 description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 6
- 238000010304 firing Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910017604 nitric acid Inorganic materials 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000002910 solid waste Substances 0.000 description 5
- -1 but in practice Chemical compound 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000011084 recovery Methods 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910001447 ferric ion Inorganic materials 0.000 description 1
- 229910001448 ferrous ion Inorganic materials 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- JWBHEXSTRWKINP-UHFFFAOYSA-L iron(2+) sulfate dodecahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.O.O.[Fe++].[O-]S([O-])(=O)=O JWBHEXSTRWKINP-UHFFFAOYSA-L 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/74—Preparation
- C01B17/76—Preparation by contact processes
- C01B17/80—Apparatus
- C01B17/806—Absorbers; Heat exchangers
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/74—Preparation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/74—Preparation
- C01B17/76—Preparation by contact processes
- C01B17/80—Apparatus
Abstract
The invention discloses a system and a method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in the steel industry. The method comprises the steps of: (1) drying the crude ferric sulfate salt crystals; (2) The ferric sulfate crystal powder is heated and decomposed to obtain sulfur trioxide, sulfur dioxide and ferric oxide, and the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing iron oxide red; (3) gas filtering and dedusting; (4) And (3) absorbing gas, namely dissolving sulfur trioxide in water to directly generate sulfuric acid, dissolving sulfur dioxide in water to generate sulfurous acid, and oxidizing the sulfurous acid in the absorption liquid into sulfuric acid by hydrogen peroxide. The system for preparing the sulfuric acid from the ferric sulfate has the advantages of large and small scale, low investment, quick response, high acceptability and strong applicability.
Description
Technical Field
The invention relates to the technical field of solid waste utilization, in particular to a system and a method for preparing sulfuric acid by pickling recovery waste ferric sulfate crude salt in the steel industry.
Background
China is a large country for producing stainless steel, and the production amount of various types of stainless steel is huge. Annealing and pickling processes are required to remove oxide scales on the surface of stainless steel by using various strong acids when producing ISI200 series and AISI300 series stainless steel strips. Sulfuric acid and nitric acid are used in the stainless steel pickling process. In order to improve the utilization rate of acid, reduce the acid consumption and reduce the pollution to the environment, the acid is generally regenerated. The stainless steel is pickled by sulfuric acid, the waste sulfuric acid containing ferrous ions in the sulfuric acid tank is generally regenerated by adopting a freezing crystallization method, and ferrous sulfate heptahydrate crystal solid waste is obtained after the waste sulfuric acid is regenerated, but the regeneration rate of the waste sulfuric acid in the sulfuric acid tank is low, and the waste water and waste materials are discharged more. The ferrous sulfate heptahydrate solid waste is calcined, sulfur dioxide generated by calcination enters a conventional sulfuric acid production system, sulfuric acid is prepared, the recovery treatment process is complex, the investment cost is high, and most stainless steel pickling enterprises are difficult to accept.
And the stainless steel is pickled by nitric acid, the waste nitric acid containing ferric ions in the nitric acid tank is regenerated by a sulfuric acid replacement method, so that the solid waste of the coarse salt crystal of the ferric sulfate dodecahydrate can be obtained after the waste nitric acid is regenerated, the treated waste acid can be fully recycled, the regeneration rate of the waste acid is high, and only the coarse salt crystal of the ferric sulfate dodecahydrate is discharged. For the crude salt crystal of the solid waste ferric sulfate dodecahydrate generated by the regeneration treatment of the waste nitric acid by adopting the sulfuric acid replacement method, the treatment system and the treatment method with convenient process, quick response, high acceptability and strong applicability are required to be provided, so that the resources are effectively utilized.
Disclosure of Invention
Aiming at the technical problems, the invention provides a system and a method for preparing sulfuric acid by recycling waste ferric sulfate coarse salt in pickling in the steel industry, which are characterized in that coarse salt crystals of ferric sulfate dodecahydrate are heated and decomposed into sulfur trioxide, sulfur dioxide and ferric oxide, the generation of sulfur dioxide is inhibited by controlling the excess air coefficient, the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing ferric oxide red, the sulfur trioxide is dissolved in water to directly generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in absorption liquid is oxidized into sulfuric acid by utilizing hydrogen peroxide, and resources are effectively utilized. The system for preparing the sulfuric acid by utilizing the ferric sulfate can be large or small in scale, is low in investment, quick in effect, high in acceptability and strong in applicability.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
the utility model provides a system for iron and steel trade pickling recovery waste material ferric sulfate crude salt preparation sulfuric acid, includes rotary kiln, sack cleaner, filler absorption tower and draught fan, the rotary kiln the sack cleaner the filler absorption tower with be connected in proper order through connecting tube between the draught fan, the kiln head of rotary kiln is equipped with spiral feeder, the kiln tail of rotary kiln is equipped with natural gas spray gun and powder export, the sack cleaner is equipped with spiral tripper, the filler absorption tower includes first filler absorption tower, second filler absorption tower and third filler absorption tower, first filler absorption tower the second filler absorption tower with the third filler absorption tower is connected through connecting tube, the draught fan is for the system provides the suction, makes the system is in negative pressure state operation.
Preferably, the lower extreme of first packing absorption tower is equipped with first air inlet, and the top is equipped with first shower nozzle, and the bottom is equipped with first absorption liquid and first spray pump, the lower extreme of second packing absorption tower is equipped with the second air inlet, and the top is equipped with the second shower nozzle, and the bottom is equipped with second absorption liquid and second spray pump, the lower extreme of third packing absorption tower is equipped with the third air inlet, and the top is equipped with the third shower nozzle, and the bottom is equipped with third absorption liquid and third spray pump, first shower nozzle the second shower nozzle with the third shower nozzle is PPH spiral atomizing shower nozzle.
Preferably, the liquid level of the first absorption liquid is controlled below the first air inlet, the liquid level of the second absorption liquid is controlled below the second air inlet, and the liquid level of the third absorption liquid is controlled below the third air inlet.
Preferably, the first packed absorption tower is provided with a first cooling system, the second packed absorption tower is provided with a second cooling system, and the third packed absorption tower is provided with a third cooling system.
Preferably, the first packing absorption tower is provided with a first liquid inlet and a first liquid outlet, the second packing absorption tower is provided with a second liquid inlet and a second liquid outlet, and the third packing absorption tower is provided with a third liquid inlet and a third liquid outlet.
The method for preparing sulfuric acid by adopting the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The method comprises the steps of (1) drying iron sulfate crude salt crystals obtained by recycling iron-containing mixed acid waste liquid in the steel industry by a parallel-flow rotary-cut hot air dryer to obtain iron sulfate crystal powder, wherein the external water content of the iron sulfate crystal powder is 1-3wt%;
(2) Heating and decomposing ferric sulfate crystal powder
Adding ferric sulfate crystal powder into a rotary kiln through a screw feeder, moving from a kiln head of the rotary kiln to a kiln tail of the rotary kiln, gradually heating, controlling the temperature of the kiln head of the rotary kiln to be 180-200 ℃, controlling the temperature of the kiln body of the rotary kiln to be 300-500 ℃, controlling the temperature of the kiln tail of the rotary kiln to be 500-750 ℃, arranging a natural gas spray gun at the tail of the rotary kiln, controlling the air excess coefficient to be 1.2 through the natural gas spray gun, ensuring that the interior of the rotary kiln is in an oxidizing atmosphere, and ensuring that the volume content ratio of sulfur trioxide and sulfur dioxide in mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is more than or equal to 99:1;
(3) Gas filtering dust-removing device
Pumping the gas and dust in the rotary kiln into a cloth bag dust remover by using a draught fan, controlling the temperature of the gas in the cloth bag dust remover to be 180-200 ℃, blocking the dust in the mixed gas outside the cloth bag by the cloth bag dust remover, and discharging the dust through a spiral discharger at the lower part of the cloth bag dust remover;
(4) Gas absorption
Under the action of the suction force of the induced draft fan, gas after dust filtration enters the first air inlet through a connecting pipeline, passes through the packing layer of the first packing absorption tower, enters the second air inlet through the connecting pipeline from the top of the first packing absorption tower, passes through the packing layer of the second packing absorption tower, enters the third air inlet through the connecting pipeline from the top of the second packing absorption tower, passes through the packing layer of the third packing absorption tower, and enters the inlet of the induced draft fan from the top of the third packing absorption tower through the connecting pipeline;
the first spray pump pressurizes the first absorption liquid and sprays the first absorption liquid downwards through a first spray nozzle at the top of the first filler absorption tower to absorb gas upwards passing through a filler layer of the first filler absorption tower, and the first cooling system controls the temperature of the first absorption liquid to be less than 75 ℃;
the second spray pump pressurizes the second absorption liquid and sprays the second absorption liquid downwards through a second spray nozzle at the top of the second filler absorption tower to absorb gas upwards passing through a filler layer of the second filler absorption tower, and the second cooling system controls the temperature of the second absorption liquid to be less than 60 ℃;
the third spray pump pressurizes the third absorption liquid and sprays the third absorption liquid downwards through a third spray nozzle at the top of the third filler absorption tower to absorb gas upwards passing through the filler layer of the third filler absorption tower, and the third cooling system controls the temperature of the third absorption liquid to be less than 45 ℃.
Preferably, the crude ferric sulfate salt crystals in the step (1) are crude ferric sulfate dodecahydrate crystals, and the external water content of the crude ferric sulfate dodecahydrate crystals is 35-45wt%.
Preferably, the drying temperature of the parallel-flow rotary-cut hot air dryer in the step (1) is set to be 250-350 ℃.
Preferably, in the step (3), the gas in the rotary kiln is sulfur trioxide, sulfur dioxide, and oxygen, nitrogen and water vapor remained by combustion, and the dust in the rotary kiln is ferric oxide powder and ferric sulfate powder.
Preferably, the first absorption liquid is purified water, the second absorption liquid is purified water, and the third absorption liquid is 0.5-1wt% of hydrogen peroxide solution.
The beneficial effects of the invention are as follows:
1. according to the invention, coarse salt crystals of ferric sulfate dodecahydrate are heated and decomposed into sulfur trioxide, sulfur dioxide and ferric oxide, the generation of sulfur dioxide is restrained by controlling the air excess coefficient, the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing ferric oxide red, the sulfur trioxide is directly dissolved in water to generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in the absorption liquid is oxidized into sulfuric acid by utilizing hydrogen peroxide, and resources are effectively utilized.
2. The scale of the sulfuric acid system for preparing the ferric sulfate can be configured according to the actual conditions of enterprises, and the method has the advantages of large and small size, low investment, quick response, high acceptability and strong applicability.
Drawings
FIG. 1 is a schematic diagram of the system architecture of the present invention;
in the figure: 1-rotary kiln, 2-bag dust collector, 3-packing absorption tower, 4-induced draft fan, 5-connecting pipeline, 11-kiln head, 12-spiral feeder, 13-kiln tail, 14-natural gas spray gun 14, 16-powder outlet, 21-spiral discharger 21, 31-first packing absorption tower, 32-second packing absorption tower, 33-third packing absorption tower, 311-first air inlet, 312-first spray head, 313-first absorption liquid, 314-first spray pump, 315-first cooling system, 316-first liquid inlet, 317-first liquid outlet, 321-second air inlet, 322-second spray head, 323-second absorption liquid, 324-second spray pump, 325-second cooling system, 326-second liquid inlet, 327-second liquid outlet, 331-third air inlet, 332-third spray head, 333-third absorption liquid, 334-third spray pump, 335-third cooling system, 336-third liquid inlet, 337-third liquid outlet.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
As shown in fig. 1:
a system for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in the steel industry comprises a rotary kiln 1, a cloth bag dust collector 2, a filler absorption tower 3 and a draught fan 4, wherein the rotary kiln 1, the cloth bag dust collector 2, the filler absorption tower 3 and the draught fan 4 are sequentially connected through a connecting pipeline 5, and the draught fan 4 provides suction force for the system to enable the system to operate in a negative pressure state.
The kiln head 11 of the rotary kiln 1 is provided with a screw feeder 12, and the kiln tail 13 of the rotary kiln 1 is provided with a natural gas spray gun 14 and a powder outlet 16. The bag-type dust collector 2 is provided with a screw discharger 21. The packed-bed absorber 3 includes a first packed-bed absorber 31, a second packed-bed absorber 32, and a third packed-bed absorber 33, and the first packed-bed absorber 31, the second packed-bed absorber 32, and the third packed-bed absorber 33 are connected by a connecting pipe 5. The filler absorption tower 3 is made of acid-resistant PPH material, and the filler layer of the filler absorption tower 3 is made of acid-resistant PPH material pall ring.
The first packed absorption tower 31 has a first inlet 311 at its lower end, a first spray head 312 at its top, a first absorption liquid 313 and a first spray pump 314 at its bottom. The lower end of the second packing absorption tower 32 is provided with a second air inlet 321, the top is provided with a second spray head 322, and the bottom is provided with a second absorption liquid 323 and a second spray pump 324. The lower end of the third packing absorption tower 33 is provided with a third air inlet 331, the top is provided with a third spray head 332, and the bottom is provided with a third absorption liquid 333 and a third spray pump 334. The first spray head 312, the second spray head 322, and the third spray head 332 are PPH screw atomizer.
The level of the first absorption liquid 313 is controlled below the first air inlet 311, the level of the second absorption liquid 323 is controlled below the second air inlet 321, and the level of the third absorption liquid 333 is controlled below the third air inlet 331.
The first packed absorber 31 is provided with a first cooling system 315, the second packed absorber 32 is provided with a second cooling system 325, and the third packed absorber 33 is provided with a third cooling system 335.
The first packing absorption tower 31 is provided with a first liquid inlet 316 and a first liquid outlet 317, the second packing absorption tower 32 is provided with a second liquid inlet 326 and a second liquid outlet 327, and the third packing absorption tower 33 is provided with a third liquid inlet 336 and a third liquid outlet 337.
Comparative example 1
The method for preparing sulfuric acid by adopting the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The crude ferric sulfate salt crystal obtained by recycling the waste liquid containing the iron mixed acid in the steel industry is crude ferric sulfate dodecahydrate crystal, and the external water content of the crude ferric sulfate dodecahydrate crystal is 40wt%. And (3) drying the crude ferric sulfate salt crystals obtained by recycling the iron-containing mixed acid waste liquid in the steel industry at 300 ℃ through a parallel-flow rotary-cut hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 2%.
(2) Heating and decomposing ferric sulfate crystal powder
The ferric sulfate crystal powder is added into the rotary kiln 1 through a screw feeder 12, and the rotary kiln head 11 moves towards the rotary kiln tail 13 and gradually rises in temperature. And in the heating process, the external water is gradually discharged, and the crystal water is gradually discharged. When the ferric sulfate crystals are heated above 480 ℃, decomposition begins. In theory, ferric sulfate crystals are heated and decomposed to generate ferric oxide and sulfur trioxide, but in practice, sulfur trioxide gas is decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the rotary kiln head 11 is controlled at 200 ℃, the temperature of the rotary kiln body 15 is controlled at 400 ℃, the temperature of the rotary kiln tail 13 is controlled at 800 ℃, the rotary kiln tail 13 is provided with a natural gas spray gun 14, the air excess coefficient is controlled at 1.0 through an air-fuel ratio valve of the natural gas spray gun 14, the interior of the rotary kiln 1 is ensured to be in an oxidizing atmosphere, and the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is 90:10;
(3) Gas filtering dust-removing device
And (3) sucking the gas sulfur trioxide, sulfur dioxide and the residual oxygen, nitrogen and water vapor generated by combustion in the rotary kiln 1 into the cloth bag dust remover 2 by using the induced draft fan 4, controlling the gas temperature in the cloth bag dust remover to be 200 ℃, blocking dust in the mixed gas outside the cloth bag by the cloth bag dust remover 2, and discharging the dust through a screw discharger 21 at the lower part of the cloth bag dust remover 2.
(4) Gas absorption
Under the action of the suction force of the induced draft fan 4, the gas after dust filtration enters the first air inlet 311 through the connecting pipeline 5, passes through the packing layer of the first packing absorption tower 31, enters the second air inlet 321 through the connecting pipeline 5 from the top of the first packing absorption tower 31, passes through the packing layer of the second packing absorption tower 32, enters the third air inlet 331 through the connecting pipeline 5 from the top of the second packing absorption tower 32, passes through the packing layer of the third packing absorption tower 33, and enters the inlet of the induced draft fan 4 through the connecting pipeline 5 from the top of the third packing absorption tower 33.
The first spray pump 314 pressurizes the first absorption liquid 313 and sprays it downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
The first absorption liquid 313 is purified water, the second absorption liquid 323 is purified water, and the third absorption liquid 333 is hydrogen peroxide with a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of the ferric sulfate crystals (calculated on a dry basis and without external water) to reach 99.5% (firing period, i.e., the material is added from the screw feeder to be discharged from the tail of the rotary kiln to be changed into ferric oxide) is 4 hours.
63.38 kg of industrial hydrogen peroxide with the consumption concentration of 27.5% per ton of dry-basis ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95%, and 5% of the hydrogen peroxide is decomposed. Namely 132.8 kg of industrial hydrogen peroxide with the consumption concentration of 27.5 percent for generating 1 ton of sulfuric acid
Example 1
The method for preparing sulfuric acid by adopting the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The crude ferric sulfate salt crystal obtained by recycling the waste liquid containing the iron mixed acid in the steel industry is crude ferric sulfate dodecahydrate crystal, and the external water content of the crude ferric sulfate dodecahydrate crystal is 35wt%. And (3) drying the crude ferric sulfate salt crystals obtained by recycling the iron-containing mixed acid waste liquid in the steel industry at the temperature of 250 ℃ through a parallel-flow rotary-cut hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 3%.
(2) Heating and decomposing ferric sulfate crystal powder
The ferric sulfate crystal powder is added into the rotary kiln 1 through a screw feeder 12, and the rotary kiln head 11 moves towards the rotary kiln tail 13 and gradually rises in temperature. And in the heating process, the external water is gradually discharged, and the crystal water is gradually discharged. When the ferric sulfate crystals are heated above 480 ℃, decomposition begins. In theory, ferric sulfate crystals are heated and decomposed to generate ferric oxide and sulfur trioxide, but in practice, sulfur trioxide gas is decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the rotary kiln head 11 is controlled at 180 ℃, the temperature of the rotary kiln body 15 is controlled at 300 ℃, the temperature of the rotary kiln tail 13 is controlled at 500 ℃, the natural gas spray gun 14 is arranged at the rotary kiln tail 13, the air excess coefficient is controlled at 1.2 through an air-fuel ratio valve of the natural gas spray gun 14, the oxidizing atmosphere in the rotary kiln 1 is ensured, and the volume content ratio of sulfur trioxide and sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is more than or equal to 99:1.
(3) Gas filtering dust-removing device
And (3) sucking the gas sulfur trioxide, sulfur dioxide and the residual oxygen, nitrogen and water vapor generated by combustion in the rotary kiln 1 into the cloth bag dust remover 2 by using the induced draft fan 4, controlling the gas temperature in the cloth bag dust remover to be 180 ℃, blocking dust in the mixed gas outside the cloth bag by the cloth bag dust remover 2, and discharging the dust through a screw discharger 21 at the lower part of the cloth bag dust remover 2.
(4) Gas absorption
Under the action of the suction force of the induced draft fan 4, the gas after dust filtration enters the first air inlet 311 through the connecting pipeline 5, passes through the packing layer of the first packing absorption tower 31, enters the second air inlet 321 through the connecting pipeline 5 from the top of the first packing absorption tower 31, passes through the packing layer of the second packing absorption tower 32, enters the third air inlet 331 through the connecting pipeline 5 from the top of the second packing absorption tower 32, passes through the packing layer of the third packing absorption tower 33, and enters the inlet of the induced draft fan 4 through the connecting pipeline 5 from the top of the third packing absorption tower 33.
The first spray pump 314 pressurizes the first absorption liquid 313 and sprays it downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
The first absorption liquid 313 is purified water, the second absorption liquid 323 is purified water, and the third absorption liquid 333 is a hydrogen peroxide solution with a mass concentration of 0.5 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of the ferric sulfate crystals (calculated on a dry basis and without external water) to reach 99.5% (firing period, i.e., the material is added from the screw feeder to be discharged from the tail of the rotary kiln into ferric oxide) is 8 hours.
6.338 kg of industrial hydrogen peroxide with the consumption concentration of 27.5% is consumed by each ton of dry ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95%, and 5% of the hydrogen peroxide is decomposed. Namely 13.28 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
Example 2
The method for preparing sulfuric acid by adopting the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The crude ferric sulfate salt crystal obtained by recycling the waste liquid containing the iron mixed acid in the steel industry is crude ferric sulfate dodecahydrate crystal, and the external water content of the crude ferric sulfate dodecahydrate crystal is 40wt%. And (3) drying the crude ferric sulfate salt crystals obtained by recycling the iron-containing mixed acid waste liquid in the steel industry at 300 ℃ through a parallel-flow rotary-cut hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 2%.
(2) Heating and decomposing ferric sulfate crystal powder
The ferric sulfate crystal powder is added into the rotary kiln 1 through a screw feeder 12, and the rotary kiln head 11 moves towards the rotary kiln tail 13 and gradually rises in temperature. And in the heating process, the external water is gradually discharged, and the crystal water is gradually discharged. When the ferric sulfate crystals are heated above 480 ℃, decomposition begins. In theory, ferric sulfate crystals are heated and decomposed to generate ferric oxide and sulfur trioxide, but in practice, sulfur trioxide gas is decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the rotary kiln head 11 is controlled at 200 ℃, the temperature of the rotary kiln body 15 is controlled at 400 ℃, the temperature of the rotary kiln tail 13 is controlled at 600 ℃, the natural gas spray gun 14 is arranged at the rotary kiln tail 13, the air excess coefficient is controlled at 1.2 through an air-fuel ratio valve of the natural gas spray gun 14, the oxidizing atmosphere in the rotary kiln 1 is ensured, and the volume content ratio of sulfur trioxide and sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is more than or equal to 99:1.
(3) Gas filtering dust-removing device
And (3) sucking the gas sulfur trioxide, sulfur dioxide and the residual oxygen, nitrogen and water vapor generated by combustion in the rotary kiln 1 into the cloth bag dust remover 2 by using the induced draft fan 4, controlling the gas temperature in the cloth bag dust remover to be 200 ℃, blocking dust in the mixed gas outside the cloth bag by the cloth bag dust remover 2, and discharging the dust through a screw discharger 21 at the lower part of the cloth bag dust remover 2.
(4) Gas absorption
Under the action of the suction force of the induced draft fan 4, the gas after dust filtration enters the first air inlet 311 through the connecting pipeline 5, passes through the packing layer of the first packing absorption tower 31, enters the second air inlet 321 through the connecting pipeline 5 from the top of the first packing absorption tower 31, passes through the packing layer of the second packing absorption tower 32, enters the third air inlet 331 through the connecting pipeline 5 from the top of the second packing absorption tower 32, passes through the packing layer of the third packing absorption tower 33, and enters the inlet of the induced draft fan 4 through the connecting pipeline 5 from the top of the third packing absorption tower 33.
The first spray pump 314 pressurizes the first absorption liquid 313 and sprays it downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
In this embodiment, the first absorption liquid 313 is purified water, the second absorption liquid 323 is purified water, and the third absorption liquid 333 is a hydrogen peroxide solution with a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of the ferric sulfate crystals (calculated on a dry basis and without external water) to reach 99.5% (firing period, i.e., the material is added from the screw feeder to be discharged from the tail of the rotary kiln to be changed into ferric oxide) is 6 hours.
6.338 kg of industrial hydrogen peroxide with the consumption concentration of 27.5% is consumed by each ton of dry ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95%, and 5% of the hydrogen peroxide is decomposed. Namely 13.28 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
Example 3
The method for preparing sulfuric acid by adopting the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The crude ferric sulfate salt crystal obtained by recycling the waste liquid containing the iron mixed acid in the steel industry is crude ferric sulfate dodecahydrate crystal, and the external water content of the crude ferric sulfate dodecahydrate crystal is 45wt%. And (3) drying the crude ferric sulfate salt crystals obtained by recycling the iron-containing mixed acid waste liquid in the steel industry at 350 ℃ through a parallel-flow rotary-cut hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 3%.
(2) Heating and decomposing ferric sulfate crystal powder
The ferric sulfate crystal powder is added into the rotary kiln 1 through a screw feeder 12, and the rotary kiln head 11 moves towards the rotary kiln tail 13 and gradually rises in temperature. And in the heating process, the external water is gradually discharged, and the crystal water is gradually discharged. When the ferric sulfate crystals are heated above 480 ℃, decomposition begins. In theory, ferric sulfate crystals are heated and decomposed to generate ferric oxide and sulfur trioxide, but in practice, sulfur trioxide gas is decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the rotary kiln head 11 is controlled at 200 ℃, the temperature of the rotary kiln body 15 is controlled at 500 ℃, the temperature of the rotary kiln tail 13 is controlled at 750 ℃, the natural gas spray gun 14 is arranged at the rotary kiln tail 13, the air excess coefficient is controlled at 1.2 through an air-fuel ratio valve of the natural gas spray gun 14, the oxidizing atmosphere in the rotary kiln 1 is ensured, and the volume content ratio of sulfur trioxide and sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is more than or equal to 100 percent.
(3) Gas filtering dust-removing device
And (3) sucking the gas sulfur trioxide, sulfur dioxide and the residual oxygen, nitrogen and water vapor generated by combustion in the rotary kiln 1 into the cloth bag dust remover 2 by using the induced draft fan 4, controlling the gas temperature in the cloth bag dust remover to be 200 ℃, blocking dust in the mixed gas outside the cloth bag by the cloth bag dust remover 2, and discharging the dust through a screw discharger 21 at the lower part of the cloth bag dust remover 2.
(4) Gas absorption
Under the action of the suction force of the induced draft fan 4, the gas after dust filtration enters the first air inlet 311 through the connecting pipeline 5, passes through the packing layer of the first packing absorption tower 31, enters the second air inlet 321 through the connecting pipeline 5 from the top of the first packing absorption tower 31, passes through the packing layer of the second packing absorption tower 32, enters the third air inlet 331 through the connecting pipeline 5 from the top of the second packing absorption tower 32, passes through the packing layer of the third packing absorption tower 33, and enters the inlet of the induced draft fan 4 through the connecting pipeline 5 from the top of the third packing absorption tower 33.
The first spray pump 314 pressurizes the first absorption liquid 313 and sprays it downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 65 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 35 ℃.
The first absorption liquid 313 is purified water, the second absorption liquid 323 is purified water, and the third absorption liquid 333 is a hydrogen peroxide solution with a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of the ferric sulfate crystals (calculated on a dry basis and without external water) to reach 99.5% (firing period, i.e., the material is added from the screw feeder to be discharged from the tail of the rotary kiln into ferric oxide) is 5 hours.
6.272 kg of industrial hydrogen peroxide with the consumption concentration of 27.5% is consumed by each ton of dry ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 96%, and the hydrogen peroxide with the concentration of 4% is decomposed. Namely 13.14 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
The temperature of the high temperature area at the tail of the rotary kiln determines the time required for the ferric sulfate dodecahydrate crystal to reach the decomposition rate of more than 99.5 percent, namely, the temperature is high, the sintering period is short, and the relative yield is high. Low temperature, long firing period and small relative yield. However, the sulfur dioxide gas content in the mixed gas is increased sharply after the temperature exceeds 750 ℃, so that the industrial dioxygen water consumption required by all the sulfur dioxide gas to generate sulfuric acid and discharging tail gas up to the standard is increased sharply, and the maximum firing temperature of the tail part of the rotary kiln is limited to be 500-750 ℃.
The temperature of the third absorption liquid 333 is controlled by the third cooling system 335 to be 35 ℃. The effective utilization rate of hydrogen peroxide is 96%, and 4% of hydrogen peroxide is decomposed. The temperature of the third absorption liquid 333 is controlled by the third cooling system 335 to be 40 deg.c. The effective utilization rate of hydrogen peroxide is 95%, and 5% of hydrogen peroxide is decomposed. The higher the temperature of the third absorption liquid 333 is, the more easily the hydrogen peroxide is decomposed. However, from the standpoint of overall economy, it is preferable to control the temperature of the third absorption liquid 333 at 40 ℃. When the temperature of the third absorption liquid 333 is controlled to 40 ℃, the third cooling system 335 may be a cold water tower.
When the third absorption liquid 333 is a hydrogen peroxide solution with a mass concentration of 0.5-1wt%, the effective utilization rate of hydrogen peroxide can reach 95% and the decomposition rate of hydrogen peroxide can be less than 5% when a trace stabilizer is added into the hydrogen peroxide solution and the temperature is controlled below 40 ℃. When the mass concentration exceeds 1%, the effective utilization rate of hydrogen peroxide can be reduced along with the increase of the concentration, and the decomposition rate of hydrogen peroxide can be increased.
The external water content in the present invention is a water content excluding crystal water.
The gas absorption principle of the invention is as follows: the lower part of the filler absorption towers is provided with absorption liquid, the liquid level is controlled at the lower part of the air inlet, the lower part of each filler absorption tower is provided with a spray pump with an inlet connected with the absorption liquid, the spray pump pressurizes the absorption liquid and sprays the absorption liquid downwards through a spray head at the top of the filler absorption tower, the absorption liquid is fully contacted with mixed gas upwards passing through a filler layer, and sulfur trioxide gas is dissolved in water to generate sulfuric acid. In order to enhance the absorption effect, the absorption liquid of each filler absorption tower is provided with a set of cooling system, and the main purpose is to cool the absorption liquid, enhance the absorption effect and reduce the generation of acid steam. The dissolution of sulfur trioxide gas in water generates sulfuric acid and releases heat. Each set of cooling system comprises 1 cooling circulating pump, 1 tube type indirect heat exchanger and 1 pipeline. The cooling circulation pump pumps the absorption liquid (dilute sulfuric acid) at the lower part of the filler absorption tower, and the absorption liquid returns to the lower part of the filler absorption tower after being cooled by the tube-in-tube indirect heat exchanger. Returning toThe gas generated by the rotary kiln comprises sulfur trioxide, sulfur dioxide, water vapor, residual oxygen and nitrogen after combustion, and the residual oxygen and nitrogen after combustion sequentially pass through the first filler absorption tower, the second filler absorption tower and the third filler absorption tower, wherein the sulfur trioxide, the sulfur dioxide and part of the water vapor are absorbed, and the residual gas contains the water vapor and the residual oxygen and nitrogen after combustion. A small amount of industrial hydrogen peroxide is added into the absorption liquid at the lower part of the third filler absorption tower, the concentration is controlled to be 0.5-1%, the absorption tower is mainly used for absorbing sulfur dioxide in residual gas, so that the content of the sulfur dioxide in the exhaust gas is within the national environmental protection control standard, and the exhaust gas reaches the standard. The reaction equation: h 2 O 2 +SO 2= H 2 SO 4 。
When the level of the absorption liquid in the lower portion of the third packed absorption tower 33 rises to the upper level line due to the absorption gas, the absorption liquid in the lower portion of the third packed absorption tower 33 may be transferred to the second packed absorption tower 32 through the third liquid outlet 337 until the level of the absorption liquid in the lower portion of the third packed absorption tower 33 falls to the lower level line.
When the liquid level of the absorption liquid in the lower part of the second packed absorption tower 32 rises to the high level line due to the absorption gas, the absorption liquid in the lower part of the second packed absorption tower 32 may be transferred to the first packed absorption tower 31 through the second liquid outlet 327 until the liquid level of the absorption liquid in the lower part of the second packed absorption tower 32 falls to the low level line.
When the liquid level of the absorption liquid in the lower part of the first packed absorption tower 31 rises to the high level line due to the absorption gas, the absorption liquid in the lower part of the first packed absorption tower 31 can be transferred to the storage tank through the first liquid outlet 317, and then the storage tank is used by adding the acid washing line.
The method mainly comprises the steps of gradually thickening the dilute sulfuric acid of the absorption liquid, wherein the concentration of the dilute sulfuric acid of the absorption liquid at the lower part of the third filler absorption tower 33 is generally controlled to be 10%, the concentration of the dilute sulfuric acid of the absorption liquid at the lower part of the second filler absorption tower 32 is controlled to be 20%, and the concentration of the dilute sulfuric acid of the absorption liquid at the lower part of the first filler absorption tower 31 is controlled to be 40%.
According to the invention, the coarse salt crystal of the iron sulfate dodecahydrate is heated and decomposed into sulfur dioxide, sulfur trioxide and ferric oxide, the generation of sulfur dioxide is restrained by controlling the air excess coefficient, the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing iron oxide red, the sulfur trioxide is dissolved in water to directly generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in the absorption liquid is oxidized into sulfuric acid by utilizing hydrogen peroxide, and resources are effectively utilized.
The system for preparing the sulfuric acid by utilizing the ferric sulfate can be large or small in scale, is low in investment and quick in effect, and can be accepted by most stainless steel pickling enterprises.
Those skilled in the art can also make appropriate changes and modifications to the above-described embodiments in light of the above disclosure. Therefore, the invention is not limited to the specific embodiments disclosed and described above, but some modifications and changes of the invention should be also included in the scope of the claims of the invention. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (5)
1. The method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in the steel industry is characterized by comprising the following steps of:
the system for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in the steel industry comprises a rotary kiln, a cloth bag dust remover, a filler absorption tower and an induced draft fan, wherein the rotary kiln, the cloth bag dust remover, the filler absorption tower and the induced draft fan are sequentially connected through a connecting pipeline, a spiral feeder is arranged at the kiln head of the rotary kiln, a natural gas spray gun and a powder outlet are arranged at the kiln tail of the rotary kiln, the cloth bag dust remover is provided with a spiral discharger, the filler absorption tower comprises a first filler absorption tower, a second filler absorption tower and a third filler absorption tower, the first filler absorption tower, the second filler absorption tower and the third filler absorption tower are connected through the connecting pipeline, and the induced draft fan provides suction force for the system, so that the system operates in a negative pressure state;
the lower end of the first filler absorption tower is provided with a first air inlet, the top is provided with a first spray head, the bottom is provided with a first absorption liquid and a first spray pump, the lower end of the second filler absorption tower is provided with a second air inlet, the top is provided with a second spray head, the bottom is provided with a second absorption liquid and a second spray pump, the lower end of the third filler absorption tower is provided with a third air inlet, the top is provided with a third spray head, the bottom is provided with a third absorption liquid and a third spray pump, and the first spray head, the second spray head and the third spray head are PPH spiral atomization spray heads;
the liquid level of the first absorption liquid is controlled below the first air inlet, the liquid level of the second absorption liquid is controlled below the second air inlet, and the liquid level of the third absorption liquid is controlled below the third air inlet; the first filler absorption tower is provided with a first cooling system, the second filler absorption tower is provided with a second cooling system, and the third filler absorption tower is provided with a third cooling system;
the first filler absorption tower is provided with a first liquid inlet and a first liquid outlet, the second filler absorption tower is provided with a second liquid inlet and a second liquid outlet, and the third filler absorption tower is provided with a third liquid inlet and a third liquid outlet;
the method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in the steel industry comprises the following steps:
(1) Drying of crude salt crystals of ferric sulfate
The method comprises the steps of (1) drying iron sulfate crude salt crystals obtained by recycling iron-containing mixed acid waste liquid in the steel industry by a parallel-flow rotary-cut hot air dryer to obtain iron sulfate crystal powder, wherein the external water content of the iron sulfate crystal powder is 1-3wt%;
(2) Heating and decomposing ferric sulfate crystal powder
Adding ferric sulfate crystal powder into a rotary kiln through a screw feeder, moving from a kiln head of the rotary kiln to a kiln tail of the rotary kiln, gradually heating, controlling the temperature of the kiln head of the rotary kiln to be 180-200 ℃, controlling the temperature of the kiln body of the rotary kiln to be 300-500 ℃, controlling the temperature of the kiln tail of the rotary kiln to be 500-750 ℃, arranging a natural gas spray gun at the tail of the rotary kiln, controlling the air excess coefficient to be 1.2 through the natural gas spray gun, ensuring that the interior of the rotary kiln is in an oxidizing atmosphere, and ensuring that the volume content ratio of sulfur trioxide and sulfur dioxide in mixed gas of sulfur trioxide and sulfur dioxide generated by heating and decomposing ferric sulfate is more than or equal to 99:1;
(3) Gas filtering dust-removing device
Pumping the gas and dust in the rotary kiln into a cloth bag dust remover by using a draught fan, controlling the temperature of the gas in the cloth bag dust remover to be 180-200 ℃, blocking the dust in the mixed gas outside the cloth bag by the cloth bag dust remover, and discharging the dust through a spiral discharger at the lower part of the cloth bag dust remover;
(4) Gas absorption
Under the action of the suction force of the induced draft fan, gas after dust filtration enters the first air inlet through a connecting pipeline, passes through the packing layer of the first packing absorption tower, enters the second air inlet through the connecting pipeline from the top of the first packing absorption tower, passes through the packing layer of the second packing absorption tower, enters the third air inlet through the connecting pipeline from the top of the second packing absorption tower, passes through the packing layer of the third packing absorption tower, and enters the inlet of the induced draft fan from the top of the third packing absorption tower through the connecting pipeline;
the first spray pump pressurizes the first absorption liquid and sprays the first absorption liquid downwards through a first spray nozzle at the top of the first filler absorption tower to absorb gas upwards passing through a filler layer of the first filler absorption tower, and the first cooling system controls the temperature of the first absorption liquid to be less than 75 ℃;
the second spray pump pressurizes the second absorption liquid and sprays the second absorption liquid downwards through a second spray nozzle at the top of the second filler absorption tower to absorb gas upwards passing through a filler layer of the second filler absorption tower, and the second cooling system controls the temperature of the second absorption liquid to be less than 60 ℃;
the third spray pump pressurizes the third absorption liquid and sprays the third absorption liquid downwards through a third spray nozzle at the top of the third filler absorption tower to absorb gas upwards passing through the filler layer of the third filler absorption tower, and the third cooling system controls the temperature of the third absorption liquid to be less than 45 ℃.
2. The method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in steel industry according to claim 1, which is characterized in that: the crude ferric sulfate salt crystal in the step (1) is crude ferric sulfate dodecahydrate crystal, and the external water content of the crude ferric sulfate dodecahydrate crystal is 35-45wt%.
3. The method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in steel industry according to claim 1, which is characterized in that: and (3) setting the drying temperature of the parallel-flow rotary-cut hot air dryer in the step (1) to be 250-350 ℃.
4. The method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in steel industry according to claim 1, which is characterized in that: and (3) the gases in the rotary kiln are sulfur trioxide, sulfur dioxide, and residual oxygen, nitrogen and water vapor generated by combustion, and the dust in the rotary kiln is ferric oxide powder and ferric sulfate powder.
5. The method for preparing sulfuric acid by pickling and recycling waste ferric sulfate crude salt in steel industry according to claim 1, which is characterized in that: the first absorption liquid is purified water, the second absorption liquid is purified water, and the third absorption liquid is 0.5-1wt% of hydrogen peroxide solution.
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| CN112707375A (en) * | 2019-10-25 | 2021-04-27 | 中石化南京化工研究院有限公司 | Method for recovering sulfur from sulfuric acid fired by sulfur-containing waste liquid |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6932002B2 (en) * | 2003-09-04 | 2005-08-23 | Recycling Solutions Technology, Llc | System and method of processing solid waste |
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| CN1994868A (en) * | 2006-12-30 | 2007-07-11 | 昆明理工大学 | Method for producing vitriol and iron ore concentrate using ferrous sulfate |
| CN102674473A (en) * | 2012-06-01 | 2012-09-19 | 湖南恒光化工有限公司 | Process for preparing ferric oxide red by adopting iron vitriol |
| CN205398139U (en) * | 2016-02-24 | 2016-07-27 | 南阳东方应用化工研究所 | Iron oxide red industry pigment dry process production facility |
| CN112707375A (en) * | 2019-10-25 | 2021-04-27 | 中石化南京化工研究院有限公司 | Method for recovering sulfur from sulfuric acid fired by sulfur-containing waste liquid |
| CN110760681A (en) * | 2019-10-31 | 2020-02-07 | 洛阳炬星窑炉有限公司 | Method for extracting sulfuric acid and nickel-chromium-iron alloy from stainless steel pickling waste liquid |
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